Service providers have traditionally implemented a physical network architecture to deploy network functions, such as Offline Charging Systems (OFCS), routers, switches, gateways, servers, etc. For example, network functions were traditionally deployed as physical devices, where software was tightly coupled with the proprietary hardware. These physical network functions have to be manually installed into the network, which creates operational challenges and prevents rapid deployment of new network functions. To address these issues, service providers are turning to a virtualized network architecture, which is referred to as Network Functions Virtualization (NFV). In NFV, a Virtualized Network Function (VNF) is the implementation of a network function using software that is decoupled from the underlying hardware. A VNF may include one or more virtual machines (VM) running software and processes on top of servers, switches, storage, a cloud computing infrastructure, etc., instead of having dedicated hardware appliances for each network function.
Software upgrades (SU) for VNFs typically take one of the following approaches. The first approach is an “in-place” software upgrade, where VMs belonging to the VNF are grouped such that each group is updated to a new release/version. This approach has the benefit that not all of the capacity of the VNF is taken out of the service at a time. On the negative side, this approach requires operator intervention and supervision through the process. The second approach is to divert the incoming traffic away to another system, drain the system to be upgraded, perform an in-place software upgrade, and then bring back the system into operation. This approach has the benefit of being quicker, because the VMs can be grouped together in larger groups, or even addressed all at once in parallel. It has the drawback that the system being upgraded is not capable of handling any traffic during the upgrade. The third approach is to set up a new system with the new software in parallel, and commission the new system into the network as the old system is drained and de-commissioned. The drawback with this approach is that it requires additional standby resources and disruptive provisioning before the new system starts handling traffic.
Network operators continue to look for effective ways of implementing a software upgrade into VNFs that implement functions such as offline charging.